JP2731223B2 - Optical disk drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an optical disk device that performs high-frequency superposition in a reproduction mode.

[Prior Art] In recent years, an optical information recording / reproducing apparatus (hereinafter, referred to as an optical disk apparatus) for recording and reproducing information by condensing and irradiating a light beam has been put to practical use. Recording / reproduction using a light beam can be performed at a higher density than a conventional magnetic head.

In an optical information recording / reproducing apparatus, a laser having excellent coherence is used as a light beam generation source, and particularly, a semiconductor laser that can be easily downsized and modulated is widely used.

By the way, when information is reproduced, it is generally known that the intensity of a laser beam is weaker than that of recording.
The intensity of the return light from the recording medium also decreases. Therefore, in order to improve the reading accuracy, it is necessary to improve the S / N. Therefore, as an example of improving the S / N, Japanese Patent Publication No. 59-9086 discloses a method of superimposing a high-frequency current of about IGHz on a laser driving current. When a high-frequency current is superimposed on the drive current of the laser, the longitudinal mode of laser oscillation is changed to multi-mode, reducing laser noise and reducing the reproduction signal.
It describes that S / N can be increased.

However, in the case of recording, since the intensity of the laser beam is high, when the semiconductor laser emits light at the peak value of the superimposed high frequency, the semiconductor laser emits light exceeding the standard value of the semiconductor laser, and the semiconductor laser is broken or deteriorated. The service life may be shortened. Therefore, as described in JP-A-62-119743, the semiconductor laser is driven to emit light by superimposing a high frequency only in the case of reproduction, and in the case of recording / erasing,
It is preferable to stop the high frequency superposition. Here, the high-frequency superimposed signal is turned off at the same time as the recording mode signal is turned on, and the high-frequency superimposed signal is turned on at the same time as the recording mode signal is turned off. In this way, even if the semiconductor laser emits a large amount of light and performs recording or erasing, the semiconductor laser emits light exceeding the standard value of the semiconductor laser, and the semiconductor laser itself is destroyed or deteriorates faster, and the life is shortened. When reproducing with weak light emission, superimposed high frequency reduces laser noise and reduces S / N.
Can be improved.

As described above, FIG. 8 shows the configuration of the control system of the light emission amount that turns off the high frequency superimposition signal when the recording mode signal is ON and turns ON the reproduction mode signal.

For example, the back light of the laser diode 2 is input to the monitor detection circuit 3, the light emission amount of which is detected, and input to the reproduction light amount control circuit 4 via the switch SW.

The reproduction light amount control circuit 4 compares the reproduction light amount with a level suitable for the reproduction light amount, and outputs an error signal to the laser drive circuit 5,
The output of the laser drive circuit 5 is output as a power supply for causing the laser diode 2 to emit light.

This laser diode 2 includes the laser drive circuit 5
A high-frequency output is supplied from the high-frequency superimposing circuit 6 to the laser drive current output from the controller.

The high-frequency superimposing circuit 6 is controlled by a high-frequency superimposing control circuit 7 for controlling high-frequency superimposition according to a control signal.

On / off of the switch SW is controlled by a reproduction APC control signal R-APC obtained by inverting the mode signal W-GATE by the inverter 15. In other words, in playback mode, this switch
When the SW is turned on, the reproduction light amount control loop via the reproduction light amount control circuit 4 automatically controls the reproduction light amount, that is, APC (automatic light amount control).

On the other hand, in the recording mode, the switch SW is turned off,
Light quantity control is performed by the recording light quantity control circuit 8. The recording light amount control circuit 8 includes a sample and hold circuit 11 that samples and holds the output of the monitor detection circuit 3 and an A / D converter 12 that converts the held value into a digital signal.
The digital signal is calculated by the arithmetic circuit 13 and compared with the indicated value in the recording light emission table, and the indicated signal is output to the laser drive circuit 5 via the indicating circuit 14 so as to match the indicated value. In this way, control is performed so that the amount of light emission in the recording mode matches the designated value. still,
In the recording mode, the drive current (reproduction current) when no light emission is performed is determined by the reproduction light amount control value held by the reproduction light amount control circuit 4.

In the recording mode, the light emission amount is not adjusted in the data section, but is written in the recording mark section provided before the data section, so as to match the indicated value. (For example, it is described in Japanese Patent Application No. 63-300882.) The operation of the above light amount control system is shown in FIG.

As shown in FIG. 9 (a), when the recording mode signal W-GATE is at "H" level, the driving mode to the laser diode 2 is increased, and at "L" level, the driving current is small. Playback mode.

For example, when data is recorded in the data portion of each sector in the recording mode, the mode is switched to the reproduction mode for a short time to read the sector address provided at the head of the sector.

The monitor current changes as shown in FIG. 9B according to the recording mode and the reproduction mode, and the recording current and the reproduction current also change as shown in FIGS. 9D and 9C, respectively.

Also, in the reproduction mode, as shown in FIG.
The C control signal R-APC becomes “H”, and at the same time, a high-frequency superimposed output is superimposed on the reproduction current and supplied to the laser diode 2 as shown in FIG.

[Problems to be Solved by the Invention] As shown in FIG. 9, for example, when switching from the recording mode to the reproduction mode, the high-frequency superimposed output is superimposed on the reproduction current level, but the rising response of the high-frequency superimposed output is low. Therefore, the reproduction current level is increased by the APC servo at the time of reproduction. When the mode is switched from the reproduction mode to the recording mode again, the reproduction light amount control current held by the reproduction light amount control circuit 4 is held as the reproduction current value when the light emission is not performed in the recording mode. Then, the recording current is added to the reproduction current to obtain a light emission current.

If the short reproduction mode period continues as shown in FIG. 9 (c), in other words, if the reproduction mode period in which high-frequency superimposition cannot respond is intermittently continued, the high-frequency superimposition current is not sufficiently superimposed. Is increased each time the mode is switched to the reproduction mode. Therefore, the reproduction current level in the recording mode is higher than the original reproduction current level. When the reproduction current level increases, the amount of recording light emission is set so that the monitor output matches the indicated value. Therefore, the amount of recording light emission decreases as the reproduction current increases. Can not do.

Even if the reproduction current level is increased intermittently by switching to the reproduction mode, the recording / light emission control value for the desired reproduction current level is set even in the recording / light emission control system which does not increase the recording current. However, if the recording and light emission are performed at the same indicated value with respect to this large reproduction current level, the condition is deviated from the appropriate condition. For this reason, the recording condition is different from the preset condition, and when data recorded under the condition is reproduced, a problem that a reading error occurs more frequently occurs.

The present invention has been made in view of the above points, and provides an optical disk apparatus that can set a recording light amount state under conditions suitable for a recording mode when switching to a recording mode even when high-frequency superimposition is performed in a reproduction mode. The purpose is to:

Means and Action for Solving the Problems In the present invention, when the mode is switched from the recording mode to the reproducing mode, the reproducing APC that turns off the automatic light amount control loop in the reproducing mode until the high frequency superimposition reaches a regular level.
By providing control means, APC is not performed while switching to the playback mode is short, fluctuations in the amount of playback during that period are suppressed, and even when switching to the recording mode, light is emitted at an amount suitable for recording conditions I can do it.

EXAMPLES Hereinafter, the present invention will be described specifically with reference to the drawings.

1 to 3 relate to a first embodiment of the present invention. FIG. 1 is a configuration diagram of a light quantity control system in the first embodiment, and FIG. 2 is a schematic configuration of an optical disk device of the first embodiment. Figure, third
The figure is a timing chart for explaining the operation of the first embodiment.

As shown in FIG. 2, the optical disk device 21 of the first embodiment
Has an optical (scientific) pickup 23 disposed opposite to an optical disk 22 that is rotated by a spindle motor (not shown). The optical pickup 23 is attached to a movable base (not shown), and moves in the radial direction R of the optical disk 22 (that is, in the direction traversing concentric or spiral tracks of the optical disk 22) by optical pickup moving means such as a voice coil motor. It's free.

The optical pickup 23 has the laser diode 2 and transmits the light beam of the laser diode 2 to the optical disk 22.
To condense and irradiate the information so that information can be recorded or reproduced. The laser diode 2 has a monitor photodetector such as a pin photodiode 25 enclosed in a housing 26. The front light of the laser diode 2 is used for recording and reproduction, while the back light is received by the pin photodiode 25, and a monitor detection circuit for controlling the light emission amount of the laser diode 2 by this photoelectric conversion output. 3.

The pickup 23 has the following configuration. The front light of the laser diode 2 is a light beam to be diffused. After being converted into a parallel light beam by the collimator lens 29, the light is incident on the polarization beam splitter 31 as, for example, P-polarized light, and is transmitted almost 100%. The transparent light of the polarizing beam splitter 31 is converted into a circularly polarized light beam by a quarter-wave plate 32, and then condensed by an objective lens 33 to irradiate the optical disk 22.

The reflected light from the optical disk 22 passes through an objective lens 33, is converted into S-polarized light by a quarter-wave plate 32, is incident on a polarization beam splitter 31, is almost 100% reflected, and is incident on a critical angle prism 34. You. The light beam reflected by the slope of the critical angle prism 34 faces the exit end face of the prism 34,
The light is received by the photodetector 35 located at the far field position.

The photodetector 35 is formed of, for example, a four-divided light receiving element, and its output is input to an addition / subtraction circuit 36, and a reproduction signal is generated by the sum (addition) of the four light receiving elements. Also, a focus error signal _FER is generated by a pair of differential outputs divided by a line parallel to the radial direction R, and a focus error signal _FER is generated by a pair of differential outputs divided by a line parallel to the tangential direction of the track. As a result, a track error signal _TER is generated. These two signals F _ER and _TER are respectively connected to a focusing coil 39, which forms a lens actuator via drive circuits 37 and 38,
A servo system that is applied to the tracking coil 41 and holds the objective lens 32 in the focus state and the tracking state is configured.

Incidentally, the light emission amount control means for controlling the light emission amount of the laser diode 2 has the following configuration.

The amount of light emitted from the laser diode 2 is inputted to the photodiode 25 forming a monitoring detection circuit 3, for example, the anode of the photodiode 25 is connected to the negative voltage source -V _c through a resistor R. The anode of the photodiode 25 has a potential corresponding to the amount of light input to the photodiode 25, and this potential is an output of the monitor detection circuit 3.

FIG. 2 shows only the configuration of the main part of the monitor detection circuit 3. In the actual monitor detection circuit, the efficiency of the laser diode 2 used is normalized, and the light emission amount and the monitor output have a fixed relationship. There is provided a compensation circuit or an adjustment circuit set so that

The monitor output of the monitor detection circuit 3 is input to a reproduction light amount control circuit 4 via a switch SW, and a reproduction light amount control signal for controlling a light emission current supplied from the laser drive circuit 5 to the laser diode 2 is output from the monitor output. Generate. The current supplied from the laser drive circuit 5 to the laser diode 2 is controlled by the control signal of the reproduction light amount control circuit 4 so that the light emission amount becomes an appropriate value. Further, in this reproduction light emission mode, the high frequency output is supplied to the laser diode 2 via the high frequency superimposition circuit 6 whose high frequency superimposition output is controlled by the high frequency superimposition control circuit 7 while being superimposed on the DC output of the laser drive circuit 5. You.

The output of the monitor detection circuit 3 is a recording light amount control circuit 8
In the recording mode, the recording light amount control circuit 8 controls the recording light amount.

By the way, the switch SW is set to the recording mode signal W-GATE.
Is turned on / off by the reproduction APC control signal R-APC output from the reproduction APC control signal generation circuit 42 to which the is input.

 FIG. 1 shows the configuration of the light amount control system.

This light amount control system uses a reproduction APC control signal generation circuit 42 different from the inverter 15 in the conventional example shown in FIG.

The reproduction APC control signal generation circuit 42
-GATE is inverted by the inverter 43 and input to the AND circuit 44, and the output obtained by comparing the output of the monitor detection circuit 3 with the reference voltage _Vref by the comparator 45 is input to the AND circuit 44, and the reproduced APC control signal R -APC is generated, and the switch SW is turned on / off by this signal R-APC.

The reference voltage _Vref is set to about the output level of the monitor detection circuit 3 when high-frequency superimposition in the reproduction mode is output at a regular level.

Therefore, immediately after switching to the playback mode,
Since the high-frequency superimposed output does not reach the normal level, the output of the monitor detection circuit 3 is also low.
Is "L" and the switch SW is OFF. When the normal level is reached, the switch SW is turned on.

The other configuration in the light amount control system shown in FIG.
This is the same as that described in the figure, and a description thereof will be omitted.

 The operation of the first embodiment will be described below.

When the recording mode and the reproduction mode are switched as shown in FIG. 3 (a), the monitor output becomes large in the recording mode and becomes small in the reproduction mode as shown in FIG. 3 (b).

Immediately after the mode is switched from the recording mode to the reproducing mode, high-frequency superimposition is performed together with the switching. However, the high-frequency superimposed output is considerably smaller than a normal level. The output is small by the amount not superimposed at the regular level, and gradually increases as the high-frequency superimposed output increases.

Therefore, when the reproduction mode is set only for a short period as shown in FIG. 3 (g) which is an enlarged view of FIG. 3 (b), the output level of the monitor detection circuit 3 does not reach the reference voltage _Vref . Therefore, the output of the comparator 45 is held at "L" as shown in FIG. Therefore, the switch SW is also kept OFF. However, if the playback mode period becomes longer,
As shown in FIG. 3 (e), the high-frequency superimposed output also increases and substantially increases toward the set level, and at the same time, the monitor output of the monitor detection circuit 3 also increases, exceeding the reference voltage _Vref . When this reference voltage _Vref is reached, the comparator
The output of 45 becomes "H", and the reproduced APC control signal R-APC outputted through the AND circuit 44 becomes "H" as shown in FIG.
And the switch SW is turned on. Thus, the reproduction light amount is controlled by the output of the monitor detection circuit 3.

In the first embodiment, when the output of the monitor detection circuit 3 has reached near the normal level in the reproduction mode (that is, the high-frequency superimposed output has reached near the normal level), the control loop of the reproduction light amount is closed. Therefore, in a short time when high-frequency superimposition is not sufficiently performed, such as in a case where the mode is switched to the reproduction mode only for a short time, light is emitted with the reproduction light amount held by the reproduction light amount control circuit 4. It is possible to prevent the reproduction light amount from fluctuating in the APC loop. For this reason, the light amount in the reproduction mode can be held at an appropriate value, and even when the mode is switched to the recording mode, the light emission amount may deviate from the appropriate value (due to fluctuations in the reproduction current in the reproduction mode). And the like can be eliminated.

FIG. 4 shows a configuration of a reproduction APC control circuit 51 according to a second embodiment of the present invention.

In this embodiment, a write mode signal W-GATE is input to a one-shot multivibrator (hereinafter abbreviated as OSM) 52, and a predetermined width T as shown in FIG. Output pulse. The output of the OSM 52 is inverted by the inverter 53 and input to the AND circuit 54.

The write mode signal W-GATE is input to an AND circuit 54 via an inverter 55, and a reproduced APC control signal R-APC is output from the AND circuit 54.
The switch SW shown in the figure is turned on / off.

OSM52 is the time constant of the resistor R and the capacitor C,
The pulse width T is set to be a value close to the time required to reach a regular level after the high frequency superposition is turned on.

 Other configurations are the same as those of the first embodiment.

In this embodiment, when the recording mode signal W-GATE is switched to the reproduction mode signal, the OSM 52 outputs a pulse having a width T. During the period when this pulse is output, the reproduction APC control signal R-APC Is not output. If the playback mode continues beyond the pulse width T, the playback APC control signal R-APC is output, the switch SW is turned on, and playback APC control is performed.

Therefore, even if the mode is switched to the reproduction mode only for a short period,
Since the reproduction light emission is performed at a constant reproduction current without performing the reproduction APC with the monitor output, the same effect as in the first embodiment is obtained.

FIG. 6 shows a configuration of a reproduction APC control circuit 61 according to a third embodiment of the present invention.

The output signal of the high-frequency superimposing circuit 6 output to the laser diode 2 is cut off the DC component by the capacitor C1 and input to the (half-wave) rectifier circuit (or detection circuit) 62. The rectifier circuit 62 includes a diode 63 and an integrating circuit 64. The integrator circuit 64 includes a resistor R2 and a capacitor C2. The rectifier circuit 62 performs envelope detection on the high-frequency signal and outputs the envelope signal to a comparator 65. This comparator 65
Outputs an “H” signal to the AND circuit 66 when the output signal level of the rectifier circuit 62 exceeds the reference voltage Vr. The other input terminal of the AND circuit 66 has a recording mode signal W-GATE.
Is inverted by the inverter 67 and input.
From 66, a reproduction APC control signal R-APC is output.

If the mode is switched to the reproduction mode for a short period as shown by the recording mode signal W-GATE as shown in FIG. 7 (a), the high frequency superimposed output does not sufficiently rise, so that the output of the rectifier circuit 62 becomes As shown in e), a signal corresponding to the rising amplitude is output. Since this output is lower than the reference voltage Vr, the output of the comparator 65 remains “L” and the
The APC control signal R-APC is not output.

On the other hand, if the period of the reproduction mode is long, the output of the rectifier circuit 62 is increased together with the rising waveform of the high frequency superimposed output,
When the high-frequency superimposed output rises to near the normal level, the output level of the rectifier circuit 62 exceeds the reference voltage Vr. Therefore, the output of the comparator 65 becomes “H”, and the reproduction APC control signal R-APC is output via the AND circuit 66.

The third embodiment has substantially the same effect as the first embodiment.

Incidentally, the light amount control system of the present invention is not limited to the one shown in FIG. 1, but may be a system for controlling the recording light amount in an analog manner, for example, as proposed in Japanese Patent Application No. 63-266450.

Further, the present invention is not limited to a write-once type device, but can be similarly applied to an erasable and recordable device such as a magneto-optical type device.

[Effects of the Invention] As described above, according to the present invention, means for detecting whether or not a high-frequency superimposed output signal rises to a normal level in a reproduction mode is provided. Turn off the automatic light intensity control in the playback mode until
Since the fluctuation of the reproduction light amount during that period is controlled, even when the mode is switched to the recording mode, the recording can be performed under the conditions suitable for the recording.

[Brief description of the drawings]

1 to 3 relate to a first embodiment of the present invention.
FIG. 2 is a block diagram of the light amount control system in the first embodiment, FIG. 2 is a schematic block diagram of the optical disk device of the first embodiment, FIG. 3 is a timing chart for explaining the operation of the first embodiment, and FIG. 5 is a circuit diagram of a reproduction APC control circuit according to a second embodiment of the present invention, FIG. 5 is a timing chart for explaining the operation of the second embodiment, and FIG. 6 is a diagram of a reproduction APC control circuit according to a third embodiment of the present invention. FIG. 7 is a circuit diagram, FIG. 7 is a timing chart for explaining the operation of the third embodiment, FIG. 8 is a configuration diagram of a light amount control system in a conventional example, and FIG. 9 is a timing chart for explaining the operation of FIG. 2 laser diode 3 monitor detection circuit 4 reproduction light amount control circuit 5 laser drive circuit 6 high frequency superposition circuit 7 high frequency superposition control circuit 8 recording light amount control circuit 42 reproduction APC control circuit

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-64-76432 (JP, A) JP-A-63-43385 (JP, A) JP-A-62-129950 (JP, A)

Claims (3)

(57) [Claims] 1. A drive circuit for supplying a drive current to a laser diode for recording and reproducing data on and from an optical recording medium, a light quantity control circuit for controlling a light emission amount of the laser diode, and a generation of the laser diode. In an optical disc device having a high-frequency superimposing circuit for reducing noise and a superimposing control circuit for controlling the high-frequency superimposing circuit, when the recording mode is switched to the reproducing mode, the high-frequency superimposing operation reaches a normal level. A reproduction APC control means for turning off an automatic light amount control loop in a reproduction mode is provided. When a transition is made from the recording mode to the reproduction mode, the monitor light for detecting the light emission amount of the laser diode reaches a predetermined value, and then the automatic light amount is controlled. An optical disk device for starting control. 2. A drive circuit for supplying a drive current to a laser diode for recording and reproducing data on and from an optical recording medium, a light quantity control circuit for controlling a light emission amount of the laser diode, and a drive circuit for generating the laser diode. In an optical disc device having a high-frequency superimposing circuit for reducing noise and a superimposing control circuit for controlling the high-frequency superimposing circuit, when the recording mode is switched to the reproducing mode, the high-frequency superimposing operation reaches a normal level. The reproduction APC control means for turning off the automatic light amount control loop in the reproduction mode is provided. When the recording mode is switched to the reproduction mode, the automatic light amount control in the reproduction mode is started after the reproduction mode continues for a certain period of time. An optical disc device characterized by the above-mentioned. 3. A drive circuit for supplying a drive current to a laser diode for recording and reproducing data on and from an optical recording medium, a light quantity control circuit for controlling a light emission amount of the laser diode, and a drive circuit for generating the laser diode. In an optical disc device having a high-frequency superimposing circuit for reducing noise and a superimposing control circuit for controlling the high-frequency superimposing circuit, when the recording mode is switched to the reproducing mode, the high-frequency superimposing operation reaches a normal level. A reproduction APC control unit for turning off an automatic light amount control loop in a reproduction mode is provided. When a transition is made from the recording mode to the reproduction mode, the output level of the high-frequency signal supplied to the laser diode from the high-frequency superimposing circuit is set to a set value. An optical disk apparatus for starting automatic light amount control in a reproduction mode when the number of optical disks exceeds a limit.